<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .container{
        width: 100vw;
        height: 100vh;
    }
    .left{
        float: left;
        width: 200px;
        height: 100%;
        background: red;
    }
    .right{
        float: right;
        width: 200px;
        height: 100%;
        background: blue;
    }
    .center{
        margin: 0 200px;
        height: 100%;
        background: yellow;
    }
</style>
<body>
    <div class="container">
        <div class="left">左</div>
        <div class="right">右</div>
        <div class="center">中</div>
    </div>
</body>

</html>